Repair questions

Fuse type from equipment safety point of view does not matter. Fuse type from audiophile point of view matters a lot. But there is no point blowing expensive fuses. Figure out your problem. Could be as simple as he started using the wrong fuse. Should be printed or etched right on the fuse. 

Tube amps are not like solid state, they do not like to be turned on without speakers connected. If that was done he may have done some damage that is now causing his current problems. Could also be the tubes are old and one or more is still working but causing the fuse blow situation. Don't know, just guessing. Won't do much harm to try running with the spare Sovteks just to see. 

If that does it, great. Enjoy! If not, I would open it up and look everything over real close for any signs of overheating or damage. At 30 years the caps could be shot. Write down values, make a shopping list, search and get some idea what you are looking at. If nothing else you will have some idea what to expect from a repair/refurbish estimate.  

Basically it is a process, and you work through the process. Here's a guy had something similar and was able to fix it himself with some help=
https://audiokarma.org/forums/index.php?threads/jolida-sj-502a.726000/

Keep in mind that tube equipment uses slow-blow fuses. If fast blow fuses are installed the amp will blow them instantly.

Sorry, misread the specs.  Yes they are slow-blow fuses.

Would it make sense to just order some cheap fuses from Amazon to use during testing/repairing?

Along with making sure speakers are connected, are there any other things to do or be aware of while testing?

Thanks!

Would it make sense to just order some cheap fuses from Amazon to use during testing/repairing?

A customer of ours recently did that and even though the ad was for slow blow fuses he got fast blow instead and blew most of them before we sorted it out. So I'd look elsewhere.